1. Field of the Invention.
This invention relates to plotter pens of the type that are used in X-Y plotter mechanisms, and particularly to a plotter pen that incorporates an improved marking fluid delivery method and structure.
2. Description of the Prior Art.
A search for pertinent prior art patents has revealed the existence of the following U.S. patents:
______________________________________ 2,711,810 4,121,224 4,015,269 4,157,552 4,274,102 4,540,993 4,540,995 4,608,576 4,736,211 ______________________________________
While the patents listed are pertinent to the subject matter of marking devices, none appear to be directed specifically to the construction of a plotter pen per se, to disposable cartridge for such a plotter pen, or to the marking fluid delivery system for such a pen.
The advent of computer graphics, computer assisted drafting, and computer assisted design has emphasized the need for a plotter pen which when inserted in the plotter pen head assembly of an X-Y plotter mechanism, will function reliably to permit initiation and continuous flow of the marking fluid contained within the plotter pen once plotting has commenced. Accordingly, one of the objects of the present invention is to provide a plotter pen that incorporates improved marking fluid delivery means interconnecting the marking fluid reservoir and the marking nib through which the marking fluid is released onto the media on which plotting is effected.
Because of the recent development of computer assisted drafting and computer graphics, only a limited number of companies have endeavored to produce X-Y plotter mechanisms, and each of these companies in most instances have tended to produce plotter pens of their own design that are dedicated to their particular X-Y plotter mechanism. As a consequence of the diversity of plotter mechanisms, there has developed a diversity in the different types of plotter pens that are available on the commercial market. It appears that the industry has not "aged" sufficiently to enable standardization and interchangeability of peripheral equipment from one X-Y plotter to another from a different manufacturer. In an attempt to accomplish such interchangeability, at least one company has specialized in the production of adaptors that make the different pens useable with different X-Y plotter mechanisms when coupled with an appropriate adaptor. Accordingly, another object of the present invention is the provision of a plotter pen design that is universally applicable in most X-Y plotter mechanisms when coupled with a new and novel adaptor system forming the subject matter of a copending application by the inventor named herein.
One of the major problems that has plagued plotter pen manufacturers on the one hand and plotter pen users on the other hand, is the tendency of the marking fluid in the pen to dry at critical locations in the delivery path between the marking fluid reservoir and the marking nib through which the marking fluid is released. Such drying of the marking fluid forms a blockage that prevents the marking fluid remaining in the plotter pen from being used unless the blockage is cleared, and this is frequently more expensive than replacing the pen with a fresh one, thus leading to a waste of the marking fluid remaining in the pen. Accordingly, another object of the present invention is the provision of a plotter pen that includes an improved marking fluid delivery system that minimizes the tendency of the marking fluid to dry within the delivery system, and which promotes complete use of all of the marking fluid within the pen.
Still another problem that has plagued the "user" industry of plotter pens is the tendency of many plotter pens to leak marking fluid once they have been removed from the X-Y plotter mechanism and laid aside for future use or for being discarded. Such a plotter pen that leaks can ruin work in progress by leaking marking fluid indiscriminately on the surface of the media being plotted. Accordingly, a still further object of the present invention is the provision of a plotter pen incorporating a marking fluid delivery system that inhibits the free flow of marking fluid from the pen when the pen is not in use.
In the operation of a plotter pen, it is desirable that the marking fluid flowing from the marking nib of the pen flow therefrom with consistency in terms of volume. Manufacturers of conventional pens attempt to achieve such consistency by inserting plungers or rods in the marking nib in an attempt to control the cross-sectional area of the passageway through which the marking fluid passes. Accordingly, another object of the present invention is the provision of an improved plotter pen in which consistent flow of the marking fluid is achieved.
With conventional pens, one of the problems that has occurred is that when a pen that has been in use is taken from the X-Y plotter and laid aside, and then subsequently picked up for reuse, the placement of the pen in a horizontal position causes displacement of the marking fluid in such a way that when the pen is again mounted for use, there is a tendency for the pen to leak, causing spills on the plotter mechanism, the operator and the media on which plotting is progressing. Accordingly, another object of the present invention is the provision of an improvement in a plotter pen which enables the plotter pen to be laid aside for a time and then be re-used without concern that the pen will leak or spill marking fluid.
I have found that one of the parameters that is extremely important in connection with the consistent flow of marking fluid from a plotter pen is the weight of the fluid in the fluid reservoir and the imposition of that weight on the incremental column of marking fluid that passes through the marking point. Accordingly, one of the important objects of this invention is the provision of a marking fluid delivery system for a plotter pen that incorporates means and a method for maintaining the weight of the marking fluid substantially constant in relation to the incremental column passing through the marking point.
There are several different types of liquid ink or liquid marking fluid pens that are available on the commercial market. Many of these pens are categorized by the type of marking fluid that they contain. For instance, there are multi-media pens which may be defined as plotter pens capable of marking on many different types of media, including paper, plastic, and foil. Other types of pens utilize inks or marking fluids that are particularly useful for etching. In this type plotter pen, the marking fluid reacts chemically with the surface of the media with which it is in contact, and thereby produces a "mark". In addition to the two foregoing types of plotter pens, there is the so-called "roller ball" pen for use in connection with special types of plotter paper. Sometimes it is not so much the type of marking fluid that is dispensed by a plotter pen that defines a difference, but the type of "nib" or "point" that is used in the plotter pen. For instance, some plotter pens include stainless steel points which are touted as useful for precision automated drafting. For matte drafting film, tungsten carbide points are touted as being effective because they provide wear resistance against the abrasive nature of the film on which the "nib" or "point" is being used.
For matte drafting film, plotter pens are provided with jewel-tipped points or carbide "points" because they provide a superior performance. One of the characteristics that is common to all of these plotter pens is that they must have a cartridge to retain the marking fluid. Again, marking fluid cartridges are made in many different configurations and sizes. Accordingly, another object of the present invention is the provision of a plotter pen that utilizes a "universal" cartridge that may incorporate any of the plotter "points" or "nibs" described above for use in special circumstances.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however, that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.